Table 2.

The effect of Hantzsch esters and other reaction parameters.^a

entry	Hantzsch ester	yield (%)b	ee (%)
1	HE-Me (1.5 equiv)	99	83
2	HE-Et (1.5 equiv)	99	91
3	HE-t-Bu (1.5 equiv)	99	96
4	HE-t-Bu (1.0 equiv)	88	96
5b	HE-t-Bu (1.5 equiv)	99	96
6b,c	HE-t-Bu (1.5 equiv)	99	96
7c,d	HE-t-Bu (1.5 equiv)	99	85

^aReaction conditions: 1a (0.1 mmol, 1.0 equiv), Hantzsch ester (1.5 equiv), CPA-6 (1 mol %), PhCF₃ (1 mL), rt, under N₂ atmosphere,12 h. The yield was determined by ¹⁹F NMR spectroscopy and the ee values were determined by chiral HPLC. ^b1 mol % of CPA-6 was used. ^cThe reaction time was 3 h. ^dThe reaction temperature was 0 °C.